Slag cement and lime are two materials that only work as a system. Slag is the fuel; lime is the match. Get the ratio right and you stabilize high-sulfate clay that lime alone would heave, using a sixth of the lime. Get it wrong and the slag sits there as filler. This page is the ratio guide and the supply page.
Send sulfate and PI. Same-day response.
TxDOT research project 0-4240 tested the ratio on a College Station clay at 20,000 ppm sulfate. The result decides the blend.
The recommended mix. Enough lime to push pH past 10.5 and wake the slag, not enough to feed ettringite. Strength 127 psi at 7 days, 198 at 28.
Same total dose, wrong split. Triple the lime and the heave comes back. The report's words: only use enough lime to catalyze the reaction of the slag.
A conventional lime job on the same soil. Strength went backwards between 7 and 28 days, 99 psi to 82.
Slag with no lime made plasticity worse, PI 41 to 47. The lime is small but it is not optional.
One percent lime controls swell but does not knock plasticity down far enough on fat clay for a working platform. On a PI 41 soil, 5:1 reached PI 27; 5:2 reached 17.
Built this way, the TxDOT researchers found a 5:2 mix performed like a 5:1 on swell. Strength barely moves with the extra lime (38 psi at 5:1, 42 at 5:2, 48 at 5:3 in that series), so the only reason to go past 1 percent is workability, and this is how you do it without paying in heave.
| Component | What it is | How it arrives |
|---|---|---|
| Slag cement | ASTM C989 Grade 100 or better, Houston producer on the TxDOT DMS-4620 list | Bulk pneumatic tanker, about 25 tons, spread dry at 5 percent |
| Lime | Quicklime or hydrated lime for slurry; commercial slurry where the job is set up for it | Slurry applied at 1 percent within four hours of the slag |
| Blend design | Ratio and dosage sized to your sulfate, PI and treatment depth | With the quote, from your geotech data |
| Paperwork | Mill certificate with fineness and SO3, producer code, SDS for both materials | With the quote |
A note on quicklime versus hydrated lime. The research used hydrated lime at 1 percent. Quicklime carries about 25 percent more available lime per ton, so an equivalent quicklime dose is a little lower. Either works; the engineer sets the number from a pH test on the actual soil.
Swell, strength, four field sites, the TxDOT construction sequence and where the sulfate is in Texas, on one page.
Loaded in Houston, delivered along I-35 from Sherman to Laredo and anywhere else in Texas.
5 parts slag cement to 1 part lime by dry weight of soil for sulfate control, per TxDOT project 0-4240. 5:2 built in two steps when a fat clay needs the plasticity down for a platform.
The TxDOT sequence applies them separately: slag dry first, then lime as slurry within four hours. That order matters because the lime slurry supplies the moisture and the pH at the moment the slag needs it. Ask us before changing it.
No. Slag needs pH above roughly 10.5 to react. Without lime it is inert filler and TxDOT testing showed it made plasticity worse.
Class C fly ash carries its own calcium and may partially activate slag, but it has not been tested on Texas soils in the published work. We treat it as a lab question, not a field recommendation.
Slag cement from a Houston producer on the TxDOT list. Lime from conflict-free suppliers or as commercial slurry near the job. Both delivered by Hasten.
Send the sulfate and PI numbers and the acreage. We will size the ratio and price both materials.
Call 832-655-7763